1/2×3 + 1/3×4 + ... + 1/49×50
= 1/2 - 1/3 + 1/3 - 1/4 + ... +1/49 - 1/ 50
= 1/2 - 1/50
=12/25
\(\frac{1}{2.3}+\frac{1}{3.4}+...+\frac{1}{49.50}\)
\(=\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+...+\frac{1}{49}-\frac{1}{50}\)
\(=\frac{1}{2}-\frac{1}{50}=\frac{24}{50}=\frac{12}{25}\)